1. Field of the Invention
A present invention relates to a power feeder system for feeding a power to a power receiving portion provided to a mobile object such as an electric vehicle in a track way type transportation system or an electric mobile, from a power feeding portion provided in a track way, a road surface or the like on which the mobile object runs.
2. Description of the Related Art
A noncontact type power feeder system is adapted to feed a power in a noncontact manner from a power feeding portion to a power receiving portion which are opposed face-to-face to each other through a gap therebetween, with the use of electromagnetic induction. The power feeding portion and the power receiving portion are provided therein with cores made of magnetic material such as ferrite. An E-shape core as an example thereof, has a plurality of protrusions and a plurality of recesses which are defined between the adjacent protrusions, and windings annularly runs around among the plurality of recesses.
Patent Document 1 (Japanese Patent Laid-Open No. 2006-128397) discloses a power feeder system for feeding a power in a noncontact manner to a shopping cart or the like. E-type cores made of ferrite are used in a power feeding portion and a power receiving portion in this power feeder system, and windings are arranged at levels equal to the heights of protrusions of the cores in both power feeding and receiving portions so as to minimize the inter distance between the windings in the power feeding portion and the windings in the power receiving portion in order to reduce leakage flux from the power feeding portion and as well to enhance the transmission efficiency from the windings on the power feeding portion side to the windings on the power receiving portion side.
Patent Document 2 (Japanese Patent Laid-Open No. 2000-150273) discloses a transformer for a noncontact type power feeder system having annular cores in a power feeding portion and a power receiving portion in order to enable transmission of a high power. The annular cores which are made of ferrite are formed in either a process in which a plurality of sector-like blocks are coupled to one another so as to form a single disc-like shape or a process in which several unit blocks having a U-like transverse sectional shape are stacked one upon another and coupled to one another so as to form a disc-like shape.
The noncontact type power feeder system disclosed in patent document 1 is adapted to be used for a relatively low power transmission for a display unit in the shopping cart or the like, but is not intended for transmission of a high power of not lower than about several ten kW. The gap between the power feeding portion and the power receiving portion is regulated so as to maintain a small value, that is, about 2 mm in order to increase its magnetic coupling rate (a ratio of an effective magnetic flux with respect to an overall magnetic flux). Should the gap be deviated within an about one millimeter, the inductance thereof would vary largely so as to be largely out of a resonance condition, and accordingly, No higher power can be transmitted effectively. Thus, this power feeder system cannot transmit a large power in this configuration as it is.
The transformer for noncontact type power feeder system, disclosed in cited reference 2, is capable of transmitting a relatively high power, having an annular core formed of sector-like blocks which are jointed to one another. However, it is difficult to form blocks having the sector-like shape, and accordingly, there is caused a problem of taking much time and labor for the manufacture thereof. Further, the core having a disc-like shape, and composed of several unit blocks having a U-like transverse-sectional shape, which are stacked one upon another and jointed to one another, causes much time and labor for manufacturing several unit blocks, and further, there is a risk of presence of gaps between adjacent unit blocks arranged in an arcuate shape, resulting in an problem of reducing a transmittable power per unit area caused by lowering of inductance due to a decrease in an area occupied by the core.
Further, since the shape of the core is annular, the winding width of the windings cannot be taken largely, resulting in decrease in magnetic coupling rate, and a large radius is required for transmission of a high power, and accordingly, there is caused a problem of lowering design flexibility.